ASSESSING SOIL COMPACTION FOLLOWING A WINTER TIMBER HARVEST IN THE WESTERN UPPER PENINSULA OF MICHIGAN

Harvesting during winter is encouraged as a best management practice to protect soil during logging operations. The western Upper Peninsula of Michigan typically experiences early and persistent snowfall, which insulates the forest floor and prevents soils from freezing. The objective of this study is to assess the effects of slash volume, snow depth, overstory treatment, and machine traffic intensity on soil bulk density following a winter harvest of a northern hardwood forest on cobbly silt-loam soils. The harvest was conducted at the Ford Forest in Alberta, Michigan using cut-to-length harvest systems (i.e. harvester and forwarder) during which the soil remained unfrozen. Four levels of machine traffic (high, medium, low, none) and two levels of overstory treatment (clear-cut and partial cut) were considered within a factorial experimental design. Samples were extracted using coring cylinders and separated into three depths (0-5, 5-10, 10-20 cm) prior to drying, sifting and weighing. Results indicate that bulk density did not differ between the no traffic treatment and low traffic treatment at the 0-5 cm depth. However, soil bulk density for the no-traffic treatment was significantly lower than soil bulk density for the medium and high traffic treatments at the 0-5 cm depth. There was a significant effect for traffic in all depths, fine and full soil, except for the 5-10 fine and full soil (which had a p-value of .06). No significant effects of slash volume or snow depth were detected but there was significant effect of percent rock at each depth